The present invention relates to expansion anchors in general, and more particularly to a metal expansion anchor sleeve, and to a method of making the same.
Expansion achor sleeves, which are used in conjunction with expander elements to anchor them in holes of a supporting structure, are already known in a great variety of different types. Usually they are made of synthetic plastic material because this permits the manufacture of such sleeves in a simple and inexpensive manner, enabling any desired configuration as to the number of slots, the provision of lugs for preventing rotation, the formation of screw threads and the like. All of this can be produced in one operation, since these plastic expansion anchor sleeves are usually produced by injection molding.
However, expansion anchor sleeves of synthetic plastic material suffer from considerable disadvantages. A particular drawback is that if they are used as elements for anchoring suspended ceilings and the like, they are readily destroyed by heat, for example in the event that fire should break out. This then permits the suspended element, such as a ceiling or the like, to drop, and to cause further damage and destruction beyond that caused by the fire.
It is also known to make expansion sleeves from metallic material. However, the prior art suggests producing these sleeves by turning them on a lathe, and this and subsequent operations which are necessary to produce such a metal expansion anchor sleeve, greatly increases the cost of manufacturing the same.